In International Patent Application No. WO 2004/016588 (the disclosure of which is hereby incorporated by reference), the present applicant disclosed a method of synthesising lactams of formulae A and B by reacting an appropriate 5-halomethylene substituted furanone with an amine under mild conditions to give lactams of general formula A, optionally followed by dehydration to give lactams of general formula B.

Each of the lactams exemplified in the specification of WO 2004/016588 included one or more bromine substituents, usually at position R3 or R4. Positions R1 and R2 were substituted with halo, alkyl (substituted or unsubstituted) or hydrogen. The lactams were shown to have antibacterial properties and to act as quorum sensing inhibitors.